Croatian population of Bosanska Krajina migrated because of Ottoman looting campaigns and later conquest. They escaped in Gorski Kotar, Istria, Kvarner, western part of Lika, Burgenland, western Hungary, NW Croatia etc.
When Ottomans conquered Bosanska Krajina it was almost empty land. Ottoman sources talk about it.
Hasan paša Predojević conquered Bihać in 1592
https://en.wikipedia.org/wiki/Telli_Hasan_Pasha
He brought settlers from his native region East Herzegovina on empty land of Cazinska Krajina, they were Muslims and Orthodoxes.
Interesting in Bosanska Krajina exist Serbs with surname Predojević who also originated from Serbian clan Predojević from Bileća area, same as Hasan paša.